subr radpsr - j.f.chandler - 1984 apr
compute pulsar pulse phase observables
in this routine 'tmdly' is used for the delay from the arrival
(free-space) at the solar-system barycenter to the observation
and may be either pos. or neg.  however, the eventually computed
observable is pulse phase.

xpp - unit vector in alpha direction from pulsar
xrho- unit vector in delta direction from pulsar
drp(1-3) - vector proper motion (rad/d)
drp(4-6) - partial of unit vector to pulsar w.r.t. ddelta
drp(7-9) - partial of unit vector to pulsar w.r.t. dalpha

iterate position of pulsar companion, if any
extra delay is conceived as pulsar "topography" passed in dstf(8)
to be subtracted from calculated delay
NOTE: if the orbit is not defined, but the delay is given in dstf(8),
that pre-computed delay is applied